In recent years, along with high integration and performance enhancement of large scale integrations (hereinafter, referred to “LSI”), new microprocessing technologies have been developed. Polishing methods based on Chemical Mechanical Polishing (hereinafter, referred to as “CMP”) (hereinafter, referred to as “CMP methods”) constitute a class thereof. A CMP method is utilized in LSIproduction processes, and is a technology that is frequently utilized particularly in the flattening of interlayer insulating materials, formation of metal plugs, and formation of embedded wirings in a multilayer wiring forming process.
For the formation of embedded wirings, a damascene method is mainly employed. That is, the damascene method is a method of forming an embedded wiring by depositing a thin film of copper or a copper alloy on an insulating material (interlayer insulating material) on which concavities (grooves) and convexities (protrusions) have been formed in advance, embedding the copper or copper alloy in the concavities, and subsequently removing the thin film deposited on the convexities (thin film in areas other than the concavities) by CMP.
On the other hand, in the under part of the wiring metal such as copper or the copper alloy, a region formed from a conductor such as, for example, tantalum, a tantalum alloy, or tantalum nitride is formed as a barrier section for preventing diffusion of the wiring metal into the interlayer insulating material or for enhancing adhesiveness. In areas other than the wiring section where the wiring metal such as copper or the copper alloy is embedded, it is necessary to eliminate the exposed barrier section by CMP. Meanwhile, the metal used in the barrier section will be hereinafter referred to as a barrier metal.
In such a damascene method, generally, polishing is carried out in plural steps such that plural kinds of CMP polishing slurries (hereinafter, may be simply referred to as “slurry”) are prepared, only the wiring metal is removed by polishing, and then eliminating only the barrier metal or the barrier metal and the interlayer insulating material by polishing. This is because since a slurry achieves polishing by a synergistic effect of a chemical action and a mechanical action, if it is desired to eliminate by polishing a particular material as a polishing object, an exclusive slurry for the particular material is required. A CMP method of polishing only the wiring metal such as described above is described in, for example, in Patent Literature 1, and a CMP method of polishing the barrier metal and the interlayer insulating material is described in, for example, Patent Literature 2.
In a slurry, various additives are added for the purpose of increasing the polishing rate with respect to a polishing object, or of enhancing the flatness of the surface after polishing. For example, Patent Literature 3 describes, in regard to a CMP method of polishing a barrier metal and an interlayer insulating material, a technology of increasing the polishing rate with respect to the interlayer insulating material and suppressing erosion or seaming by incorporating a methacrylic acid-based polymer into the slurry.
In recent years, application of the CMP technology in a wider variety of applications as a result of the progress in the LSI forming technology and the slurry used in CMP. Furthermore, even for conventional applications, since new materials are being applied to the conductive material, the barrier metal, the interlayer insulating material and the like, there are available a wide range of the polishing object for the CMP method.
As the range of applications of CMP has been broadened as a result of the emergence of new polishing object, the slurry is required to have new polishing characteristics. For example, a polishing method of removing the polishing object at a high polishing rate and stopping polishing at an arbitrary thickness should be carried out such that a substrate having a stopper is provided in the under part of a polishing object, the polishing object is removed using a slurry, and polishing is terminated at the time point where the stopper is exposed. However, in the damascene method, the polishing method of stopping polishing using a stopper is usually not carried out, and therefore, a slurry suitable for that purpose has not been developed, either. For example, in regard to the conventional slurries described in Patent Literatures 1 to 3, the respective polishing rates with respect to metal and interlayer insulating material are described, but nothing has been mentioned about polishing a substrate having a material such as a stopper, in addition to the above-described materials.